Table of Content

31 December 2002, Volume 20 Issue 4

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Articles

A Theoretical Study on the Thawing of Biological Tissue Induced by Laser Irradiation

ZHOU Jian-hua, LIU Deng-ying, XU Jian-zhong, HUAI Xiu-lan

2002, 20(4):  331-335. 

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This paper describes a numerical model for the thawing of biological tissue induced by laser irradiation. The light propagation was calculated by seven-flux model. The solid-liquid phase change heat transfer was simulated by the equivalent heat capacity method. The program code was validated against a test problem and good agreement was obtained. Finally, the model was used to study the effects of the optical properties of tissue and the laser irradiation parameters on the thawing process of the biological tissue induced by laser heating.

The Temperature Field in a Current-Carrying Plate with a Curve Crack

YANG Chun-yan, BAI Xiang-zhong

2002, 20(4):  336-340. 

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The temperature field in a current carrying plate with a penetrated curve crack under the action of transient pulse current was calculated and analyzed by using complex function analysis solution. Singularity character of the current around the crack tip was obtained. The point heat source was formed, so that the temperature field around crack tip could be deduced. The result of theoretical calculation was consistent with the experiment. It was the basis for defining the stress field around the crack tip.

Gait Optimization Based on Genetic Algorithm for a Biped Robot Climbing Upstairs

KE Xian-xin, GONG Zhen-bang, WU Jia-qi

2002, 20(4):  341-345. 

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A seven-link biped robot model was chosen for gait stability optimization in climbing upstairs. Motions of the feet during a regular step were designed by the 3^rd order spline; motions of the hip were designed through acceleration analysis, and the locus of ZMP was obtained by computing the dynamic model. Thus the gait stability of the biped robot could be shown as a multi variable optimal problem in connection with the placement and the pose of the upper body of the robot. Finally, genetic algorithm (GA) was applied to get the optimal solution. The simulations of the biped robot climbing upstairs showed that the method work satisfactorily.

Time-Fuel Synthetic Optimal Trajectory Planning for Robots

ZOU Ji-gang, ZENG Zhao-long, ZHANG Rui, LIU He, LI Wen-xiu

2002, 20(4):  346-349. 

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In this paper, robots paths are approached by B-spline through introducing pseudo-distance and pseudo-velocity variables to parameterize the path. We also use dynamic programming carry out two-dimension dynamic optimization and find the time-fuel synthetic optimal trajectory for robots.

Study of a Robust Adaptive Control Scheme with Backstepping

SU Bing-wei, CAO Yun-feng, CHEN Xin, YANG Yi-dong

2002, 20(4):  350-353. 

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The adaptive backstepping approach based on turning function is improved in this paper. A new robust adaptive flight control system is designed for a certain unmanned aerial vehicle (UAV). First, the system model of the UAV is changed to a disturbed strict feedback system, which contains nonlinear parameter uncertainty, uncertain nonlinear and unmodeled dynamics. Second, a Lyapunov function with an adaptive regulating term to the general error is presented and then a stable adaptive control law and parameter update law is derived. There is a robust adaptive term, which can compensate the effect of uncertain nonlinear and the unmodeled dynamics both in the control law and parameter update law. The adaptive regulating term to the general error also appears in the control law and parameter update law, its main function is to slow the parameter update rate when the actuator saturation occurs. At last, this new flight control system is tested by simulation.

A Study on the Giant Magnetostrictive Microdisplacement Actuator with a Displacement Sensing Function

JIA Zhen-yuan, YANG Xing, WANG Fu-ji, GUO Dong-ming, GUO Li-sha

2002, 20(4):  354-359. 

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A giant magnetostrictive microdisplacement actuator which has the function of sensing its displacement and which uses a new type of functional materials (giant magnetostrictive materials) as its microdisplacement device has been developed. A microdisplacement closed-loop control system is also built. A kind of circular membrane flexible structure with high distinguishability, zero friction, and integrated sensing-transferring-displacement capability, is proposed to be used as a mechanism to transfer and sense the actuator's microdisplacement. The analysis formulas and the distribution curves of deflection and variance ratio of strain are obtained by using circular plate bending theory. On basis of this, the distribution of the sensors that sense the actuator's displacement is obtained, and the actuator's displacement-sensing function is realized. At the same time, experimental studies on the actuator and its microdisplacement closed-loop control system are carried out. The results show that the sensitivity of the actuator and the precision of the system's closed-loop control are improved.

The Design and Simulation of Neural Network Adaptive Programming Control for AC Drive System

WANG De-ming, LIU Xian-xing, WANG Li-min

2002, 20(4):  360-364. 

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A Hopfield neural network is used as an adaptive control of the AC drive system. The dynamic output of the speed controller is programmed through neural network, so that the speed controller has a good robustness against the variation of parameters. By adding the parameter auto tracking neural networks, a double neural network adaptive programming control model with the function of on-line parameter tracking is constructed to overcome the uncontrollable load torque. Simulation results show that this system is capable of good dynamic performance.

Fault Diagnosis for Nonlinear Systems Based on Linearization Technique

CHEN Yu-dong, SHI Song-jiao, WENG Zheng-xin

2002, 20(4):  365-368. 

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A fault diagnosis method based on linearization technique for nonlinear closed-loop stable systems is proposed. It first linearizes the original system on its working point using linearization technique and designs state observer for the linearized systems so that the initial estimates for fault signals can be obtained. Then the ultimate estimates for fault identification are obtained through the correction based on the relation between the error of state observe and that of state estimate. Simulation results demonstrate its validity.

Conceptual NC Grinding Wheel Dressing Based on NURBS

LÜ Ke, GENG Guo-hua, ZHOU Ming-quan

2002, 20(4):  369-372. 

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ANC preliminary design paradigm is put forward through analyzing and calculating the normal unit vector of the NURBS surface. By exploiting typical modules, such as the translating module, the rotating module and the base module, the NC movement conceptual configuration is precisely expressed. This conceptual module is recorded in the computer. By the introduction of agent, the creative preliminary design is realized and the interpolation control technique is completed in the course of grinding wheel dressing.

A New Dual-Polarized Aperture-Coupled Microstrip Patch Array

CUI Jun-hai, ZHONG Shun-shi, DUAN Wen-jun, LU Biao, XIE Ya-nan

2002, 20(4):  373-376. 

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A new dual polarized aperture-coupled microstrip antenna array is proposed. Based on the analysis of the finite-difference time-domain (FDTD) method, the design of an 8×2 array is presented and investigated. The thickness of the array is only 1.8mm. The experimental results show that the bandwidth of VSWR<1.5 reaches 4.8%, and the cross polarization level is better than-23dB, while the isolation between the dual polarization ports is 30dB. This array can be used as a sub array of spaceborne synthetic aperture radar (SAR) system by connecting it with the active transmitter/receiver (T/R) components.

Feature-Based Face Recognition by Elastic Graph Matching

SUN Da-rui, WU Le-nan

2002, 20(4):  377-381. 

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A feature-based elastic graph matching algorithm (FEGM) on the basis of the Lades' elastic graph matching face recognition algorithm is proposed in this paper. It includes two steps. First, the face feature such as eye, nose, mouth are localized by Gabor transforms, and a group of feature vectors composed by Gabor coefficients is extracted. Then the FEGM algorithm is performed to make the total cost function as small as possible, recognition result on Yale face database shows that recognition rate has been improved substantially.

A Real-Time Middle ware Platform for Monitoring Transactions on the Stock Exchange

ZHANG Yun-yong, HU-Jian, LIU Jin-de

2002, 20(4):  382-386. 

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With the development of the stock market, it is necessary to have a corresponding monitor platform to capture irregular transactions. In order to acquire the real-time, reliable and highly extensive characteristics, a highly available real-time surveillant middleware platform for transactions on the stock exchange based on the mobile agent is developed. Its structure and operation are explained and experiment data given to show its unique features.

A Kalman-Filter Method for Power Control in WCDMA

YANG Wei, CHENG Shi-xin

2002, 20(4):  387-390. 

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A Kalman-filter method for power control is recommened for broadband packet switched CDMA wireless networks. Temporal correlation of interference can be observed when data are being sent continuously by transmitters. A Kalman filter can then be used to predict interference power. Based on the predicted interference and estimated path gain between the transmitter and receiver, transmission power is determined to achieve the desired signal-to-interference-plus-noise ratio(SINR). Simulation results reveal that the Kalman-filter method for power control provides a performance improvement.

A Study on the Data Streams of the PHY Sub-Layer in the Dedicated Multimedia Fiber Industrial Network

LI Jin-hui, SUN Xiao-han, ZHANG Ming-de, DING Dong

2002, 20(4):  391-395. 

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A novel dedicated multimedia fiber industrial network (FIN) established by consulting the protocols and standards of FDDI-Ⅱ satisfies the specific requirements of real-time data transmission. In this paper, the services of FIN are classified and the cycle frame structure is determined. The processing mechanism of the PHY sub-layer is analyzed and the transmitting and receiving flow charts are presented. The data streams of a simulated frame processed in the PHY sub layer are illustrated on the basis of the service partition and processing schemes.

The Application of Sigma-Delta Modulator in Digit Fractional Divider

ZHANG Si-zhong

2002, 20(4):  396-398. 

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This article analyses the improvement to S/N of Sigma-delta. It introduces the application of sigma-delta in A/D for digit fractional divider, and describes the improvement to output phase vibration in fractional divider due to the application of sigma-delta. The conception of replacing multiple accumulators with repeatedly cycled utilization of a sigma-delta accumulator is raised.

A Method to Reduce the PAPR of the OFDM System Based on BCM

SONG Tie-cheng, YOU Xiao-hu, SHEN Lian-feng

2002, 20(4):  399-403. 

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The problem of the practical orthogonal frequency division multiplexing (OFDM) system is that the peak to the average power raito (PAPR) is very high. This paper briefly describes the progress researches on reducing the PAPR. The method to reduce the PAPR of the OFDM system based on block coding modulation (BCM) is presented and the construction of large sub carrier number systems is proposed. We have analyzed the implementation principle and carried out computer simulation. The results indicate that the BCM method not only can effectively lower the PAPR in the OFDM system, but also carry out forward error correction (FEC).

A New Integrated Spread-Spectrum System of Communication and Wireless Location with Eight Phases Space-Time Modulation

SONG Mao-zhong, XU Zong-ze

2002, 20(4):  404-408. 

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To meet the challenge of future mobile communication and integrated communication and wireless location systems, a new spread spectrum communication system with eight phases space-time modulation technology is proposed to transmit azimuth and communication message. The spectrum, capacity and bit error rate of this system are similar to the spread-spectrum QPSK. The paper suggests a method of matrix to describe the principle of modulation. The key technical problems such as modulation, transmitting array antennae, demodulation, carry recover and direction-finding are solved, by taking into consideration the orthogonal metrics and the fact that a walsh sequence wⁿ is orthogonal to (-1) ^n-1 wⁿ.

Reverse Link Performance Simulation of a Fixed-Point cdma2000 1x

ZHAO Jun-hui, ZHAO Chun-ming, YOU Xiao-hu

2002, 20(4):  409-412. 

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In this paper, we discuss the principle of the Rake receiver for cdma2000 1x reverse link. The fixed-point simulation platform is also developed by COSSAP. We compare the simulation performance between fixed-point and float-point and study the degradation due to the finite word length implementation of the Rake receiver and viterbi decoder with various A/D quantizers for a cdma2000 1x reverse link.

Research Notes

On the Chaotic Nature of Internet Traffic

ZHANG Jin-gang, LI Hui, XU Pei-xia

2002, 20(4):  413-415. 

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The chaotic time series analysis is used to study Internet traffic. Through reconstruction of phase space and calculation of maximum Lyapunov exponent, we find that Internet traffic is chaotic. This establishes the theoretic foundation for analyzing and modeling Internet traffic using chaos theory.

Fast Convergence Pattern on Many Spaces for DPM with Optimal Parameters and Its Application to Electromagnetic Field Problems in the Multi Branch Domains

SUN Lian-you, HONG Wei

2002, 20(4):  416-418. 

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In order to effectually solve the electromagnetic field problems in the complex multi branch domains, this paper presents the fast convergence pattern on many spaces for decomposition projective method (DPM) with optimal parameters. The design and formula of the optimal parameters are also given. Practical application shows that the convergence rate is quicker than DPM. The iterative number of the fast convergence pattern with optimal parameters decreases greatly-about one third of that of DPM, and the efficienty is raised.

The Application of Frequency Domain Dynamic Compression to FMCW Millimeter-Wave Radar

LI Yu-fang, XIA Guan-qun, SUN Xiao-wei

2002, 20(4):  419-422. 

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An efficient frequency domain dynamic compression method has been developed for the anticollision system. This method, based on a frequency cancellation technique, is able to remedy the primary shortcomings of the FMCW radar-the leaked signal from the transmitter and the complex configuration of circuits. It can restrain the strong interference signal and substitute the AGC to some extent.

The Online Use of Image Processing Technology in Detecting Printing Registration Deviation

YANG Yong-yue, DENG Shan-xi, HE Ge-qun

2002, 20(4):  423-425. 

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In this paper, the design and analysis of the components of an image measuring system based on image analysing is investigated. The authors measured the planar geometrical parameters through image processing and applied these to the "detecting system against registration deviation in color printing" to detect and control the registration deviation online.

The Application of Wavelet Analysis in Hydrological Sequence Trend Analysis

XUE Xiao-jie, JIANG Xiao-hui, HUANG Qiang, WANG Yu

2002, 20(4):  426-428. 

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We decompose the hydrological sequence made of different frequencies into the low and high frequencies in the multi-resolution analysis according to the characteristic of hydrological sequence frequencies and then restore the deoxidize trend components according to the reconstruct principle of wavelet coefficients, in order to judge the hydrological sequence trend. The result of a study based on the gauged yearly flow of the Yellow River, shows that the mode is feasible.

Quasi Sliding Mode Control Based on Inverse Dynamics Fuzzy Neural Networks

FU Chun, XIE Jian-ying

2002, 20(4):  429-431. 

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For ordinary uncertain nonlinear systems, a scheme of quasi sliding mode control based on a fuzzy neural networks of inverse dynamics is proposed, the control could be obtained through the feed forward inference of the fuzzy neural networks. Simulations indicate the method's effectiveness.

A Study on Integrated Controllers with Fuzzy Control and PID Control and Their Simulations

CHENG Qi-ming

2002, 20(4):  432-434. 

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Three integrated controllers with Fuzzy control and PID control are discussed. They can overcome the shortcomings of either Fuzzy control or PID control used singly and improve the control performance and robustness.